The restaurant industry's opposition to a higher minimum wage is hardly a secret--it's one of the top issues on the lobbying agenda of the National Restaurant Assn., the chain restaurants' Washington trade group.

The mystery is why the industry seemed so loath to reveal its role in a round-robin letter signed by more than 500 economists, including four Nobel laureates, calling the proposed minimum-wage hike to $10.10 an hour a "poorly targeted anti-poverty measure."